Field of the Invention
The present invention relates to a light source unit including laser diodes as light sources and a microlens array and a projector.
Description of the Related Art
In these days, data projectors are used on many occasions as an image projection system which projects an image of a screen of a personal computer or a video image, as well as images based on image data which is stored on a memory card on to a screen. Conventionally, the mainstream of these data projectors has been those which utilize a high-intensity discharge lamp as a light source. In recent years, however, there have been proposed projectors that use power-saving, long-life and high-intensity laser diodes.
A projector disclosed in Japanese Unexamined Patent Publication No. 2013-190591 (JP-2013-190591A) includes, as light sources, a blue laser oscillator that emits light in the blue wavelength range, a red laser oscillator that emits light in the red wavelength range, and a luminescent light emitting device that emits light in the green wavelength range as a result of excitation light being shone on to a luminescent material layer. Axes of light in the blue wavelength range and light in the red wavelength range intersect an axis of light in the green wavelength range at right angles, and a dichroic mirror is disposed in the position where the axes of the blue and red lights intersect the axis of the green light at right angles. This dichroic mirror transmits the light in the blue wavelength range and the light in the red wavelength range and reflects the light in the green wavelength range so as to emit the blue, red and green lights in the same direction. The lights emitted from the dichroic mirror are passed through a microlens array to obtain diffusive light whose intensity is distributed uniformly and are then guided to a display device.
In the projector disclosed in JP-2013-190591A, the lights emitted from the laser diodes and the luminescent light from the luminescent light emitting device are passed through the same microlens array. Generally speaking, light emitted from a laser diode has strong directionality and a narrow illumination range.
Because of these characteristics, in case laser light is incident on a microlens array that is adjusted to the incident range of light in the green wavelength range that is luminescent light, the laser light is shone on to a small number of microlenses, and hence, even though the laser light that has passed through the microlens array is superposed, there have been situations where the uniform intensity distribution is not achieved to a sufficient level.
Additionally, in case smaller microlenses are used to enhance the uniformity of laser light, the loss of transmitted light is increased by joint portions between the microlenses, resulting in a reduction in utilization efficiency of light.
The invention has been made in view of the problems inherent in the projector of the related art, and an object of the invention is to provide a projector in which the light efficiency of a light source is improved.